The present invention relates generally to a rotary encoder, and more particularly, to a rotary encoder for electrically detecting a signal corresponding to a rotation quantity of a cylindrical or hollow rotary body.
A rotary encoder proposed by the present applicant in Japanese Patent Laid-Open Application No. 63-81212 is typical of a measuring device for measuring a rotation quantity of a cylindrical rotary body.
The rotary encoder is a simply constructed excellent measuring device capable of measuring the rotation quantity of the cylindrical rotary body with a relatively high resolving power.
This advantage is attainable by the following arrangement. An interior (hollow portion) of the rotary body incorporates an image forming optical system. A grating image in a first region on a side surface of the rotary body is projected on a grating in a second region on a side surface opposite to the first region with respect to a rotary axis of the rotary body.